1. Field of the Invention
The present invention relates to a vehicle display apparatus.
2. Description of the Related Art
A vehicle having a head-up display (HUD) as an indicator is being developed. A HUD can present information, such as vehicle speed, car-navigation guidance information (e.g., arrows for routing assistance), and information notifying the presence of a pedestrian at nighttime, for example. A vehicle on which a HUD is mounted can also incorporate a meter (see, for example, Japanese Examined Utility Model Registration Application Publication No. 6-001471).
The technique described in this literature commonly switches luminance of a meter 12 and that of a HUD 15 at daytime by the use of an up/down switch 3 (see, for example, 28-41 lines in the left-hand column of page 3) and adjusts the display luminance of the HUD based on the display luminance of the meter at nighttime (see, for example, 24-50 lines in the right-hand column of page 3). This aims to automatically set balance between the nighttime luminance of the meter and that of the HUD at a suited one (see, for example, 2-7 lines in the left-hand column of page 4).
As described above, at both daytime and nighttime, when the luminance of the HUD is adjusted, the luminance of the meter is also adjusted. Thus, it is impossible to individually set the luminance of the meter and that of the HUD, and this may impair usability. For the technique described in the above literature, because the luminance of the HUD depends on the setting made by the up/down switch at daytime and is set according to the luminance (specific value) of the meter at nighttime, the influence of the outside of the vehicle is not reflected. However, the display luminance of the HUD is preferably controlled according to illuminance outside the vehicle irrespective of daytime or nighttime. If the HUD simply has individually set values of daytime luminance and nighttime luminance, it is difficult to achieve sufficient usability.